The purpose of this project is to investigate the role of epileptic seizures in oxidative stress. There is a wealth of research that demonstrates that epileptic seizures lead to the formation of reactive oxygen and nitrogen species (ROS and RNS), which cause oxidative damage to DNA, lipids, and proteins. The role of excitotoxic events during epileptic seizures and the subsequent formation of ROS and RNS leading to oxidative stress will be investigated. Microdialysis sampling in discrete brain regions along with simultaneous recording of electrocorticographic (ECoG) activity will be used to probe chemical and electrographic activity changes in the brain associated with seizures. This will provide the ability to correlate biomarker levels with seizure activity. Microdialysis sampling will be used to continuously monitor several biochemical pathways prior to, during, and after induction of seizures. Microdialysis experiments will provide both temporal and spatial information about oxidative stress caused by seizures and the brains response to them. This approach will provide insight into questions that have remained unclear using plasma and urine sampling and standard tissue sampling techniques. Methods previously developed in the PI's laboratory will be used to monitor formation of ROS and RNS, biomarkers for DNA damage and lipid peroxidation, and the neurotransmitter amino acids and catecholamines. A new analytical method will be developed to detect prostanoids resulting from arachidonic acid metabolism. Three experimental models of epilepsy will be used in Wistar rats. The first two models use 3-mercaptopropionic acid (3-MPA) to chemically induce seizures in a controlled manner. For one model the 3-MPA is systemically administered and in the other it is locally administered through the microdialysis probe. A chemical kindling model will then be used, where a sub-threshold dose (for triggering seizures) of pentylenetetrazol will be used to generate seizures of increasing intensity, culminating in a generalized seizure convulsion. In addition, we propose to investigate the role of various modulation agents on the release of known oxidative stress agents during epileptic seizures. Using microdialysis sampling coupled to the advanced analytical methodology, the neurological events leading from seizures to oxidative stress will be investigated. In particular, the temporal relationship between oxidative stress (as measured by ROS and RNS formation), and neuroexcitation (as measured by the GABA/glutamate ratio and the catecholamines) will be determined and correlated to the duration and intensity of seizure episodes.